In accordance with the progress of wireless communication techniques, wireless communication systems having various standards have been being developed. Wireless communication systems are designed to support user terminals accessing a backbone network through an air channel. That is, from the point of view of the end-to-end elements which are a service user and a service provider, it does not matter which standard is employed by a wireless communication system in using contents. Accordingly, a technique for maintaining a satisfactory condition of an air connection by enabling the performance of a seamless handover between different networks of different mediums is being studied.
There exists the Institute of Electrical and Electronics Engineers (IEEE) 802.21 Media Independent Handover (MIH) as a typical technique for handover between different networks. The handover between different networks is called a vertical handover. According to the MIH, event service, command service and information service are defined for vertical handover. The event service denotes recognizing change of physical information in air access link, the command service denotes handling control commands for the vertical handover, and the information service denotes managing network information on different networks. Accordingly, a mobile terminal (MT) gets proper network information by using services as stated above, and performs the vertical handover.
Network information for the vertical handover is provided by an information server (IS), which is a separate entity in a wireless communication system. The IS manages network information on a plurality of networks, and provides the network information upon a request from the MT. IEEE 802.21 MIH standard defines a list of the network information, which has to be maintained at the IS. However, ways for getting, maintaining, updating and managing the network information and a structure of the IS for the ways are not defined. Therefore, there is a need to provide the structure of the IS for supporting vertical handover in a practical wireless communication environment.